Abstract:
Microbial induced calcite precipitation for self-healing purpose in concrete is governed by several factors including type of bacteria and the carrier compound. In order to investigate the autonomous healing, this study presents a comparison between calcite precipitation activity of B. subtilis KCTC-3135T, B. cohnii NCCP-666 and B. sphaericus NCCP-313 and explores the potential application of natural fibers as carriers for bacteria in concrete. For crack remediation, bacteria embedded in coir, flax and jute fibers were introduced in concrete. Calcium lactate pentahydrate and urea were incorporated as organic nutrients. For each formulation, specimens were prepared to evaluate mechanical, microstructural and visual properties of self-healing concrete. The results suggest that B. sphaericus NCCP-313 precipitated more calcium carbonate as healing agent which is reflected by higher compressive strength, ultrasonic pulse velocity and better healing characteristics. In terms of carriers, coir fibers resulted in highest compressive strength, while flax fibers were more efficient in regaining compressive strength and improving ultrasonic pulse velocity.
